14 research outputs found
Strangeness in the cores of neutron stars
The measurement of the mass 1.97 +/- 0.04 M_sun for PSR J1614-2230 provides a
new constraint on the equation of state and composition of matter at high
densities. In this contribution we investigate the possibility that the dense
cores of neutron stars could contain strange quarks either in a confined state
(hyperonic matter) or in a deconfined one (strange quark matter) while
fulfilling a set of constraints including the new maximum mass constraint. We
account for the possible appearance of hyperons within an extended version of
the density-dependent relativistic mean-field model, including the phi-meson
interaction channel. Deconfined quark matter is described by the color
superconducting three-flavor NJL model.Comment: 6 pages, 2 figures, contribution to "Strangeness in Quark Matter
2011", Cracow, September 18-24, 201
Finite-size effects at the hadron-quark transition and heavy hybrid stars
We study the role of finite-size effects at the hadron-quark phase transition
in a new hybrid equation of state constructed from an ab-initio
Br\"uckner-Hartree-Fock equation of state with the realistic Bonn-B potential
for the hadronic phase and a covariant non-local Nambu--Jona-Lasinio model for
the quark phase. We construct static hybrid star sequences and find that our
model can support stable hybrid stars with an onset of quark matter below and a maximum mass above in agreement with recent
observations. If the finite-size effects are taken into account the core is
composed of pure quark matter. Provided that the quark vector channel
interaction is small, and the finite size effects are taken into account, quark
matter appears at densities 2-3 times the nuclear saturation density. In that
case the proton fraction in the hadronic phase remains below the value required
by the onset of the direct URCA process, so that the early onset of quark
matter shall affect on the rapid cooling of the star.Comment: version to match the one published in PR
High efficiency contactless energy transfer system with power electronic resonant converter
Neutron star matter in a modified PNJL model
We discuss a three-flavor Nambu-Jona-Lasinio model for the quark matter equation of state with scalar diquark interaction, isoscalar vector interaction and Kobayashi-Maskawa-t Hooft interaction. We adopt a phenomenological scheme to include possible effects of a change in the gluon pressure at finite baryon density by including a parametric dependence of the Polyakov-loop potential on the chemical potential. We discuss the results for the mass-radius relationships for hybrid neutron stars constructed on the basis of our model EoS in the context of the constraint from the recently measured mass of (1.97 +- 0.04) M (J ) for the pulsar PSR J1614-2230
Characteristics of hybrid compact stars with a sharp hadron-quark interface
We describe two aspects of the physics of hybrid stars that have a sharp
interface between a core of quark matter and a mantle of nuclear matter.
Firstly, we analyze the mass-radius relation. We describe a generic "Constant
Speed of Sound" (CSS) parameterization of the quark matter equation of state
(EoS), in which the speed of sound is independent of density. In terms of the
three parameters of the CSS EoS we obtain the phase diagram of possible forms
of the hybrid star mass-radius relation, and we show how observational
constraints on the maximum mass and typical radius of neutron stars can be
expressed as constraints on the CSS parameters.
Secondly, we propose a mechanism for the damping of density oscillations,
including r-modes, in hybrid stars with a sharp interface. The dissipation
arises from the periodic conversion between quark matter and nuclear matter
induced by the pressure oscillations in the star. We find the damping grows
nonlinearly with the amplitude of the oscillation and is powerful enough to
saturate an r-mode at very low saturation amplitude, of order , which
is compatible with currently-available observations of neutron star spin
frequencies and temperatures.Comment: 15 pages, 12 figures. Published versio